Bump requirement to Qt 5.15.2

Qt 5.15.2 includes API that makes transitioning to Qt 6 easier.
We currently have workarounds for Qt 5.14 in place that we can
remove when requiring 5.15.2, and we also can stop adding workarounds
for new code.

Change-Id: I920fdccc41d755a6ad39cb5161cd916999fee755
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Robert Löhning <robert.loehning@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

README.md

@@ -35,7 +35,7 @@ https://doc.qt.io/qtcreator-extending/coding-style.html
 
 Prerequisites:
 
-* Qt 5.14.0 or later
+* Qt 5.15.2 or later
 * Qt WebEngine module for QtWebEngine based help viewer
 * On Windows:
     * MinGW with GCC 7 or Visual Studio 2017 or later

cmake/QtCreatorAPI.cmake

@@ -3,7 +3,7 @@ if(QT_CREATOR_API_DEFINED)
 endif()
 set(QT_CREATOR_API_DEFINED TRUE)
 
-set(IDE_QT_VERSION_MIN "5.14.0")
+set(IDE_QT_VERSION_MIN "5.15.2")
 
 include(${CMAKE_CURRENT_LIST_DIR}/QtCreatorAPIInternal.cmake)
 include(${CMAKE_CURRENT_LIST_DIR}/QtcSeparateDebugInfo.cmake)

doc/qtcreatordev/src/qtcreator-documentation.qdoc

@@ -472,9 +472,6 @@
 
     You can configure documentation builds using CMake or qmake.
 
-    \note Since \QC version 4.12, only Qt 5.14.0 or later is supported
-    for building documentation.
-
     For more information about setting up the build environment with a
     self-built Qt if you do not want to build the whole Qt, see
     \l{https://wiki.qt.io/Building_Qt_Documentation}{Building Qt Documentation}

qbs/imports/QtcProduct.qbs

@@ -29,7 +29,7 @@ Product {
             enableFallback: false
         }
     }
-    Depends { name: "Qt.core"; versionAtLeast: "5.14.0" }
+    Depends { name: "Qt.core"; versionAtLeast: "5.15.2" }
     Depends {
         name: "Qt.core5compat"
         condition: usesQt6

qtcreator.pro

@@ -1,9 +1,9 @@
 include(qtcreator.pri)
 
 #version check qt
-!minQtVersion(5, 14, 0) {
+!minQtVersion(5, 15, 2) {
     message("Cannot build $$IDE_DISPLAY_NAME with Qt version $${QT_VERSION}.")
-    error("Use at least Qt 5.14.0.")
+    error("Use at least Qt 5.15.2.")
 }
 
 include(doc/doc.pri)